On assembly lines in the automotive industry, vehicle air conditioning systems (MAC's mobile air conditions) are filled with coolant. This filling is carried out by filling systems, which automatically enable the entire filling process in adaptation to the vehicle air conditioning system. The coolants used pose a strain to the environment, are partially combustible and often produce hazardous decomposition products. For this reason, there are high safety requirements on the tightness of such filling systems, so that coolant discharges can be excluded or diagnosed.
Since coolants are liquefied gases, states of matter and pressure levels must be considered. In particular, a temperature-induced rise in pressure in lines and equipment of such filling systems must be taken into account in design. Even an amount of coolant released in the event of an accident should be limited in order to prevent or minimize risks with regard to a harmful explosive atmosphere.
Filling systems are characterized by an integrated vacuum and filling circuit with means for sensing vacuum, pressure, and mass determination, a media supply section that is fed from bottles or tanks, an adapter device for connecting the filling interface in the vehicle, and a control system that initiates the automatic filling sequence. The pressure test, evacuation, leak test, post-evacuation, filling, and coolant suck back functions are combinable partial functions of a typical overall process. This process is mainly performed at assembly lines in the reworking, tryout, and vehicle development departments.
It is the object of the invention to provide a method for operating filling systems for coolants which in particular meets the following requirements:
1. Limitation of coolant discharge quantities in the event of a failure or accident
2. Prevention and limitation of harmful explosive atmospheres when working with combustible coolants or coolants that are environmental or health hazards
3. Protection of hydraulic circuits from too high pressures
4. Prevention of coolant discharge from relief valves
5. Diagnosis of leaks
This object is achieved with the technical features according to claim 1 and advantageous embodiments, as described in the dependent claims; essential features and advantages include:
The method according to the invention for preventing and detecting coolant discharges from complex hydraulic systems is characterized in that a circuit that carries coolant is divided into small volumes having stop valves and one relief valve. Leak detection diagnosis can be performed in a simple manner using a pressure sensor that can be integrated in the system. As a result, required explosion protection precautions and restrictions that were required in the filling environment can be reduced.
Activation of the relief valves is prevented by removing pressure or volume into an accumulator used by all clusters and by decoupling the clusters from one another using check valves. The accordingly designed clusters—which will be explained in greater detail with reference to the drawing—can be integrated in the hydraulics of the filling system. It is also possible that these clusters form an integral part of the hydraulic system for configuring the functions of the overall process.
Continuous leak diagnosis can be performed using the pressure measuring equipment in each cluster, both during the operation of the filling system and the filling process itself and during the service life of the system and beyond.
Furthermore, the requirements listed above (as described under requirements numbered 1 to 5) can be achieved in that technically leak tight systems will achieve a “permanently leak tight” state with the measures mentioned. At the same time, filling systems equipped with these features have to meet reduced requirements with respect to explosion protection precautions to be taken.
Another advantage of this method is that the pressure measuring equipment in conjunction with exhaust systems provides for a more sensitive leak detection compared to installing additional gas warning sensors because the actual gas warning sensors are adversely affected by the air change rates.
Finally, regular leak detection with pressure measuring equipment in conjunction with ventilation equipment and gas warning sensors may form a part of measures with which technically leak tight systems can be reclassified as permanently leak tight systems. This results in operating cost savings for the operator, e.g. when troubleshooting with the doors open and the system running.
Decisive advantages of the overall method therefore include limitation of the development of harmful explosive atmospheres in working areas and reduction of measures from otherwise typical requirements for Ex zones as well as the reduction of such zones. Furthermore, the requirements the method has to meet do not obstruct the actual filling process and the required components can be directly integrated in the hydraulic circuits of the filling system or even form a functionally determined part thereof.